D. M. Krzeminska

Feasibility of soil moisture estimation using passive distributed temperature sensing

Through its role in the energy and water balances at the land surface, soil moisture is a key state variable in surface hydrology and land?atmosphere interactions. Point observations of soil moisture are easy to make using established methods such as time domain reflectometry and gravimetric sampling. However, monitoring large?scale variability with these techniques is logistically and economically infeasible. Here passive soil distributed temperature sensing (DTS) will be introduced as an experimental method of measuring soil moisture on the basis of DTS. Several fiber?optic cables in a vertical profile are used as thermal sensors, measuring propagation of temperature changes due to the diurnal cycle. Current technology allows these cables to be in excess of 10 km in length, and DTS equipment allows measurement of temperatures every 1 m. The passive soil DTS concept is based on the fact that soil moisture influences soil thermal properties. Therefore, observing temperature dynamics can yield information on changes in soil moisture content. Results from this preliminary study demonstrate that passive soil DTS can detect changes in thermal properties. Deriving soil moisture is complicated by the uncertainty and nonuniqueness in the relationship between thermal conductivity and soil moisture. A numerical simulation indicates that the accuracy could be improved if the depth of the cables was known with greater certainty.

Techniques for the modelling of the process systems in slow and fast-moving landslides

This chapter reviews some of the current strategies for landslide modelling. Main physical processes in landslides are first recalled. Numerical tools are then introduced for the analysis of the behaviour of slow- and fast-moving landslides. Representative case studies are introduced through the chapter to highlight how different modelling strategies can be used depending on the physical processes that the modeller wants to take into account.

Innovative Techniques for the Characterization of the Morphology, Geometry and Hydrological Features of Slow-Moving Landslides

In the last 10 years, landslide characterization has benefited from numerous developments in remote sensing, near surface geophysics, instrumentation and data processing. This section highlights various advances and innovative techniques or processing methods to characterize the morphology, structure and hydrological features of landslides. Airborne Laser Scanner (ALS) technique has emerged as a promising tool for characterizing slope morphology, with the perspective of automatic detection of landslide-affected areas. Combining ALS-data DTM with geophysical and geotechnical information has allowed to reconstruct the 3D landslide geometry considering data uncertainty and resolution. This is a significant forward step in landslide investigation. Of major importance is also the detection and monitoring of water infiltration in the sliding masses, using indirect prospecting techniques such as ERT and distributed temperature sensing (DTS) using fibre-optic cables. These new techniques could be a major help in understanding the water paths and in designing appropriate remediation systems. Finally, although most of these results have been obtained in clayey landslides, the applied methods can be extended to other landslide types, with some technical adaptations.

Sprinkling Tests to Understand Hydrological Behaviour of Mudslide

The unsaturated zone buffers precipitation and controls groundwater recharges. Quantification of groundwater recharges is important for the improvement of hydrogeomorphological hazard analysis. The importance of fast preferential flow is recognized in literature, but its quantification remains difficult.